CLIMAT devices have been used for more than three decades to monitor atmospheric corrosivity. These units have been utilized successfully around the world in marine and industrial type atmospheres. The procedure was originally called a "wire-on-bolt" test, because the devices consist of a copper or steel bolt around which an aluminum wire is wrapped [1].
CLIMAT apparatus prior to exposure, Al wire wrapped on (from left to right), Nylon, Steel, and Copper rod.
The Al-Steel and Al-Cu, wire and bolt combinations have varied sensitivities depending upon the atmosphere. This is due to the variation in the galvanic corrosion between the materials. It has been reported [2] that the Al-Cu combination responds strongly to both marine and industrial sites, whereas the Al-Steel combination responds strongly only to marine sites and is relatively indifferent to industrial sites.
The percent mass loss from the Al-Steel combination is generally regarded as the marine corrosion index (MCI) and the percent mass loss from the Al-Cu combination is generally regarded as the industrial corrosion index (ICI). The percent mass loss from the Al-Nylon combination is known as the atmospheric corrosivity index (ACI). Based on the MCI the following classification of marine atmospheres has been proposed:
Classification of Marine Atmospheres Based on the MCI index
MCI Range
Classification
Significance
0-2
Negligible
Average Habitable Area
2-5
Moderate
Seaside
5-10
Moderately Severe
Seaside and Exposed
10-20
Severe
Very Exposed
>20
Very Severe
Very Exposed, Wind and Sand Swept
The Kingston area has a strong historical connection with the CLIMAT units. The Aluminum Company of Canada (ALCAN) started preparing "wire-on-bolt" tests in their Kingston Research and Development Center in the early 1960's and gave them the name CLIMAT units.
Des Doyle worked at ALCAN for 35 years, the majority of those years spent working as a corrosion specialist. He has extensive experience in preparing CLIMAT units and in interpreting exposure data. Des (now retired) has agreed to act as an "adviser" in the CLIMAT corrosivity testing service of the Corrosion Doctors.
More Corrosion Doctors pictures
1. ASTM Standard Designation :G 116-93, "Standard Practice for Conducting Wire-on-Bolt Test for Atmospheric Galvanic Corrosion" (back)
2. D.P. Doyle and T.E. Wright, Rapid Methods For Determining Atmospheric Corrosivity and Corrosion Resistance, Chap. 16, Atmospheric Corrosion, edit. by W.H. Ailor, John Wiley and Sons, 1982. (back)
